It is well-known that fungi are a large group of nongreen plants that receive their energy and raw materials through parasitic habits. Fungi are dependent upon the organic food made by photosynthesizing green plants. They represent a constant and ever present threat to many agricultural crops ranging from tropical and semi-tropical vegetation to temperate climate crops. The control of fungi has been achieved through the use of a heterogeneous group of chemicals termed "fungicides" that mitigate, inhibit or destroy fungi. Such fungicides have been applied by spray or dust applications of protective or eradicative amounts of the material to the locus of the fungi to be controlled.
The bacteria, also, form a well-known class of microscopic plants having round, rod-like, spiral or filamentous single-celled or non-cellular bodies which are often aggregated into colonies or motile by means of flagella. Bacteria live in soil, water, or organic matter, in the bodies of plants and animals, and are autotrophic, saprophytic, or parasitic in nutrition. Bacteria can be either helpful or harmful to mankind and are often used by man to his advantage. It is often desirable and necessary to control bacteria to prevent damage to organic matter. As such, bactericides perform a valuable function in the control or eradication of unwanted bacteria.
The compositions of this invention are particularly valuable as bactericides when applied to the locus of bacteria to be controlled in an effective amount. The method and amount of composition applied to effect bactericidal control is similar to the fungicidal method and amount. Consequently, the presented invention will be described more particularily with respect to the fungicidal use because such use has been more extensively investigated and is the preferred use. This, however, is not to in any manner limit the scope of the present invention, but rather is a manner of more clearly setting forth the preferred embodiments of the present invention.
Prior to about 1939, inorganic sulfur and copper compounds were used almost exclusively as sprays and dust fungicides. Copper and mercury compounds were also used as applications in seed treatments. As early as 1882, copper sprays were introduced as a Bordeaux mixture for the control of downy mildew on grapes. The Bordeaux mixture consisted of a light blue gelatinous precipitate suspended in water and formed by reacting 4 parts of copper sulfate to 4 parts of hydrated lime (calcium hydroxide) in 50 gallons of water. Various variations in the composition of the resulting mixture have been made by changing the ratio of the components.
While copper compounds have been known for their ability to control fungi, soluble copper compounds are known to be extremely toxic to vegetation. Consequently, the copper materials applied must be relatively non-toxic to the plants while being effective fungicides. As such, it is necessary, in order to have an effective fungicide, to have an insoluble copper material in finely divided form which can be effectively applied to vegetation in a manner whereby it will adhere to the vegetation while remaining non-toxic to the vegetation to which it is applied. The finer the copper compound, the more surface area it can cover and therefore, in general, the more effective it will be per unit weight.
It is well-known that various materials, including copper compounds, can be milled to extremely fine particle size such that the surface area of the particle becomes extremely large. With finely milled material, theoretically such material is able to cover massive surface areas with relatively small amounts of copper compound. As a practical matter, it is extremely difficult to disperse and/or redisperse such finely milled copper materials because of the tendency of fine particles to agglomerate such that the finely divided particles are not fully dispersed but rather accumulate as larger particles, thus greatly reducing the effectiveness and surface area of the material.
It has been discovered that an effective way of producing the required finely divided dispersant of copper values is to precipitate the copper values in situ. Under certain desirable conditions, copper can be made to precipitate in the desired finely divided state. However, it is also well-known that the more desirable copper solutions are corrosive, particularly visa brass. For example, copper chloride is used as an etchant. Cuprammonia is known to be a much more powerful corrosive than either copper or ammonium ions individually. With the corrosive nature of copper solutions, it is particularly parenthetical that brass is the most widely used material for fungicidal spraying equipment, particularly the pumps, valves and nozzles used in such equipment. This corrosiveness is well documented by Rumford, Chemical Engineering Materials, 1st American Edition, pp. 194.
If the ammonia in a spray-type cuprammonia fungicide solution is bound by simply changing the pH, then as the pH of 7 is approached on the alkaline side, the copper quantitatively turns to an insoluble form which settles to the bottom of the storage containers. On the other hand, if the copper is prevented from precipitating with chelating agents such as EDTA (ethylene diamino tetra acetate), it will not deposit the active adherent form of copper required to protect the vegetation.
It is, therefore, an object of the present invention to provide a cuprammonia low carboxylate solution which is substantially noncorrosive to metal surfaces.
It is another object of the present invention to provide a cuprammonia low carboxylate solution which is readily hydrolizable to insoluble copper form which is fungicidally active.
It is another object of the present invention to provide a cuprammonia low carboxylate material which, on hydrolysis, forms a finely divided flocculent precipitate of copper values which, when applied to vegetation, forms a gelatinous coating which adheres tenaciously to the vegetation.
It is yet a further object of the present invention to provide an effective fungicidal composition which comprises finely divided copper values which are not readily removed by the subsequent application of moisture such as dew or rainfall.
These and other objects of the present invention will become readily apparent from the description of the invention which follows.